Oh, to be Michelle Williams. The lucky, lucky actress steams up the October cover of W magazine alongside her "Blue Valentine" costar Ryan Gosling. Seriously, look at that cover. Sigh. Inside the mag, the pair are quite candid about filming their gritty romantic drama, including dishing on their heated sex scene.

While it's probably many a girls' dream to hit the sheets with the 29-year-old actor, for Michelle, the experience was less than ideal. "We never rehearsed anything, and those were really dark days," she recalled. "We shot the beginning of our relationship first, and it was fun and alive. Then we did the sex scenes and it was…toxic. Ryan and I had stopped relating to each other as Ryan and Michelle. Those scenes took forever. I had a long drive from set to home each night, and I would roll down all the windows and turn up the music as loud as I could and hang my head out the window like a dog and scream. It was my escape."

Ryan, too, found the sex scenes taxing. "You mean the trying-not-to-have-sex sex scene? It was hard…a lot of times actors can trick people into thinking something is happening when it’s not happening, and we had to call ourselves out on anything that didn’t feel honest," Ryan said. "Actors become very professional and proficient about watching out for each other’s light and not stepping on each other’s lines. All of these things are artificial, and you have to strip that away if you’re going to achieve a sense of intimacy. In real life sex is messy, and we wanted to get at that wonderful messiness."

Considering how much buzz the film garnered at this year's Sundance Film Festival, it's surprising how long "Blue Valentine" actually took to get made. Both stars stuck around through the arduous process because they believed in the film's potential.

"A project like 'Blue Valentine' took years to get off the ground, and I was able to stick with it," Michelle said. "I first read the script when I was 21, 22, and it became my reason for being for the longest time. When I ran into Ryan, he said, 'What about that movie?' I was surprised; I thought 'Blue Valentine' existed only in my head. Until he said that, I was worried it wasn’t quite as good as I had thought. He validated my reaction."

"It took forever; for four years 'Blue Valentine' would be ready to go, and then the film would fall apart again due to financing or timing," Ryan remembered. "It was always me and Michelle—I think Michelle was involved for five or six years. Finally, the planets aligned and we shot it last summer in Pennsylvania. The director, Derek Cianfrance, had us living as these characters."

In fact, Ryan lived so much in his character, that he filmed an entire scene fast asleep! "Once, I fell asleep in the middle of a take, and we filmed through it," he said. "After I woke up, Michelle said, 'We did the scene, and we filmed you sleeping on the couch.'"

How hot are Ryan and Michelle's pictures? Are you even more excited to see "Blue Valentine" now?